C.t. Grayson, MD, MPH, Wendy Kurata, MS, Karen Matsumoto, Lisa Pierce, DSc. Tripler Army Medical Center
Objectives: Gulf War Illness (GWI) is a chronic, multisystem illness marked by cognitive and mood dysfunction that affects up to 30% of GW veterans. The diagnosis remains elusive, useful treatments are lacking, and the cause is poorly understood, although exposures to pyridostigmine bromide and pesticides are consistently identified among the strongest risk factors. Rodent studies determined that exposure to physiologically relevant doses of neurotoxic chemicals and stress results in spatial learning and memory impairments, increased depressive-like behavior, and partial neuron loss/reduced neurogenesis in the hippocampus. Previous work in our laboratory using the same rat model identified a persistent elevation of microRNA-124 (miR-124) levels in the hippocampus whose gene targets are involved in cognition-associated pathways including synaptic plasticity, neurogenesis, and neuroendocrine signaling. The overall goal of this study is to determine whether inhibition of miR-124 by intracerebroventricular (ICV) infusion of a miR-124 inhibitor improves deficits in learning and memory, mood, synaptic and neuroendocrine function in an established rat model of GWI. The purpose of this project was to establish stereotaxic coordinates for ICV cannula placement and effective doses for endogenous miR-124 inhibition.
Methods: Injection of dye into the brain cannulae of 7 male rats was used to verify stereotaxic coordinates localizing the right lateral ventricle and delivery into the ventricular system. Subsequently, 13 rats were implanted with osmotic pumps containing miR-124 inhibitor with delivery rates of 0, 0.1, 0.5, 1.0 and 5.0 nmol/day (n=3 for all except n=1 for 5.0 nmol/day). Brains were harvested after 14 days and analyzed by quantitative PCR to examine expression levels of endogenous miR-124 and 12 validated mRNA targets, and by western blot for known protein targets.
Results: Dose-dependent reduction of miR-124 was observed in the hippocampus, cerebellum, and cortex (p=0.026, 0.036, 0.051, respectively; ANOVA), with significant decrease occurring at the lowest dose. Evaluation of known miR-124 targets at the mRNA and protein level is ongoing. Reduced weight gain was observed at doses higher than 0.1 nmol/day indicating possible off target effects.
Conclusion: ICV infusion of miR-124 inhibitor is a feasible approach to evaluate the therapeutic efficacy of miR-124 inhibition in a rat model of GWI. Our group is currently pursuing reversal of behavioral and epigenetic changes in treated rats. This work will help to determine whether inhibition of miR-124 is a promising therapeutic approach to alleviate the learning and memory dysfunction and depression associated with this debilitating illness in GW veterans.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 78405
Program Number: MSS09
Presentation Session: Full-Day Military Surgical Symposium – Basic Science Presentations
Presentation Type: MSSPodium